AB0553 KIDNEY BIOPSY IN FIRST RENAL FLARE OF SLE – WHAT DOES IT TELL US?
Authors: L. Karlsson, A. Zickert, E. Svenungsson, I. Gunnarsson
Journal: Annals of the Rheumatic Diseases (2022)

Background Lupus Nephritis (LN) is an immune-complex mediated glomerulonephritis affecting up tp 60% of all SLE patients during the disease course. A kidney biopsy is indicated in SLE patients presenting with signs of renal involvement, such as persistent proteinuria, and is generally recommended to evaluate the inflammatory findings but also to rule out other etiologies of renal involvement and to guide the need of immunosuppressive therapy. Objectives To investigate the histopathologic findings in first-time renal biopsies from a large cohort of SLE patients. We especially evaluated the type and occurrence of histopathological findings other than LN as these may lead to a risk of inadequate therapeutic interventions. Methods Patients from the Karolinska SLE cohort who had a first-time onset of renal involvement from 1995 to 2021 and subsequent renal biopsy were included in the study. All patients fulfilled the American College of Rheumatology (ACR) and/or Systemic Lupus Erythematosus International Collaborating Clinics (SLICC) disease classification criteria (1, 2) for SLE and were biopsied on clinical indication, i.e., proteinuria &gt; 0.5 g/day or active SLE in combination with a rise in plasma creatinine, decrease in glomerular function or new onset proteinuria with concurrent active urine sediment. Results In total, 141 patients with first time presentation of renal involvement who had been subject to renal biopsy were included. Of these 107 patients (75.9 %) were female. The median age at the time of biopsy was 34.5 years (range 15.5 - 86.4). For more patient baseline characteristics, see Table 1. One-hundred twenty-five patients (88.7 %) had findings consistent with LN according to ISN/RPS classification system. Twenty-five patients (18.4 %) had class I - II, 43 (30.5 %) class III ± V, 31 (22.0 %) class IV ± V and 26 (18.4 %) class V. Sixteen patients (11.3 %) did not have histological changes in accordance with LN. Of these, 3 had hypertensive nephrosclerosis, 2 had antiphospholipid associated nephropathy, 1 had IgA nephropathy, 1 had tubulointerstitial nephritis and 7 had evidence of systemic vasculitis. Of these, 5 were later found to be ANCA-positive and were re-diagnosed with concomitant ANCA-associated vasculitis. Two patients did not show any classifiable histological changes. Of the 16 non-LN patients, 6 had proteinuria &gt; 0.5 g/day, 2 had new-onset low-grade proteinuria and concurrent active urine sediment, 2 had new-onset low-grade proteinuria with concurrent increasing SLE disease activity, and 5 patients had isolated persistent low-grade proteinuria. In one case data was missing. Table 1. Baseline characteristics, 141 patients Age at SLE diagnosis (years); M (IQR) 32.2 (22.0 – 44.9) SLE duration at biopsy (years); M (IQR) 0.6 (0.2 – 5.3) Systolic blood pressure (mm Hg); Mean (SD) 127.5 (20.8) Ethnicity Caucasian; n (%) 119 (84.4) Asian; n (%) 9 (6.4) African; n (%) 7 (5.0) Hispanic; n (%) 6 (4.3) Prednisone equivalent dose (mg/day); M (IQR) 10.0 (0–20.0) Diagnosis according to ISN/RPS Class I-II 25 (17.7) Class III ± V 43 (30.5) Class IV ± V 31 (22.0) Class V ± II 26 (18.4) TMA/antiphospholipid syndrome 2 (1.4) Vasculitis 7 (5.0) Hypertensive nephrosclerosis 3 (2.1) IgA nephropathy 1 (0.7) Tubulointerstitial nephritis 1 (0.7) Nonspecific changes 2 (1.4) Conclusion We demonstrate that renal histopathology confirmed other causes than LN in a significant proportion (11.3 %) of SLE patients with signs of renal involvement. Since these patients may need other therapeutic interventions than patients with classic LN, we can conclude that the renal biopsy is important in order to guide the choice of therapeutics. References [1]Tan, Eng M, et al. “The 1982 revised criteria for the classification of systemic lupus erythematosus.” Arthritis &amp; Rheumatism: Official Journal of the American College of Rheumatology 25.11 (1982): 1271-1277. [2]Petri, Michelle, et al. Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus. Arthritis &amp; Rheumatism 64.8 (2012): 2677-2686. Disclosure of Interests None declared